Ankyramorpha

Ankyramorpha ("anchor forms") is a proposed clade of early stem reptiles which lived between the early Cisuralianepoch (middle Sakmarian stage) and the latest Triassicperiod (latest Rhaetian stage) of Africa, Antarctica, Asia, Australia, Europe, North America and South America.^[2][3]

This clade was named in a 1996 parareptile study by Michael deBraga and Robert R. Reisz. They provided the name Ankyramorpha for a newly recognized clade encompassing "the most recent common ancestor of Procolophonia (including pareiasaurs and procolophonoids, among others) and Lanthanosuchoidea (which includes and Acleistorhinidae and Lanthanosuchidae) and all its descendants", and this clade name sees continued use among modern parareptile studies.^[4][5][6] A similar name, Hallucicrania, was provided in an earlier 1995 study by Michael S. Y. Lee, who defined it as the node-based taxon formed by the most recent common ancestor of lanthanosuchids and "pareiasauroids" (pareiasaurs + Sclerosaurus), and all its descendants. Unlike Ankyramorpha, which explicitly included procolophonoids, Hallucicrania was originally designed to exclude procolophonoids, which Lee's analysis argued to have split off prior to the divergence between lanthanosuchids and pareiasaurs.^[7] Nevertheless, purely considering the taxa encompassed by their definitions, Hallucicrania and Ankyramorpha refer to an identical grouping.

The following cladogram is simplified after the phylogenetic analysis of MacDougall and Reisz (2014) and shows the placement of Ankyramorpha within Parareptilia. Relationships within emboldened terminal clades are not shown.^[6]

Algunos estudios desde principios de la década de 2020 en adelante han cuestionado la validez de Ankyramorpha (y Parareptilia en general), encontrando que Procolophonia no está relacionado con los bolosáuridos, lantanosúquidos y acleistorrínidos. ^{[ 8 ]} Otros estudios han recuperado un Ankyramorpha que solo incluye a Acleistorhinidae y Procolophonia como un grupo monofilético, y Lanthanosuchus como ni siquiera un reptil. ^{[ 9 ]} Cladograma según Jenkins et al. 2025, con "parareptiles" resaltados en naranja: ^{[ 9 ]}